Durability of FRP Composites for Construction

Durability of FRP Composites for Construction
ISIS Educational Module 8: Durability of FRP Composites for Construction Produced by ISIS Canada

FRP Composites For Construction Module Objectives To provide students with a general awareness of important durability consideration for FRPs To facilitate and encourage the use of durable FRPs and systems in the construction industry To provide guidance for students seeking additional information on the durability of FRP materials ISIS EC Module 8

Cold Temperatures & Freeze-Thaw
FRP Composites For Construction Outline Introduction & Overview Case Study Moisture & Marine Exposures Specifications Alkalinity & Corrosion Reduction Factors High Temperatures & Fire Fatigue Cold Temperatures & Freeze-Thaw Creep UV Radiation ISIS EC Module 8

Introduction & Overview
FRP Composites For Construction Introduction & Overview Section: 1 The problem: In recent years, our infrastructure systems have been deteriorating at an increasing and alarming rate New materials that can be used to prolong and extend the service lives of existing structures ?? Fibre Reinforced Polymers (FRPs) ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Key uses of FRPs in construction: Internal reinforcement of concrete Corrosion of steel reinforcement in concrete structures contributes to infrastructure deterioration Use non-corrosive FRP reinforcement External strengthening of concrete Provide external tension or confining reinforcement (FRP plates, sheets, bars, etc.) ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 What is FRP? FRP is a composite: Composite = combination of two or more materials to form a new and useful material with enhanced properties in comparison to the individual constituents (concrete, wood, etc.) High-strength fibres FRPs consist of: Fibres Matrix Polymer matrix ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Polymer matrix Polymer matrix: As the binder for the FRP, the matrix roles include: Binding the fibres together Protecting the fibres from environmental degradation Transferring force between the individual fibres Providing shape to the FRP component ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Polymer matrix Commonly used matrices: Internal reinforcing applications Vinylester: fabrication for FRP reinforcing bars (superior durability characteristics when embedded in concrete) External strengthening applications Epoxy: strengthening using FRP sheets/plates (superior adhesion characteristics) ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Fibres Fibres: Provide strength and stiffness of FRP Protected against environmental degradation by the polymer matrix Oriented in specified directions to provide strength along specific axes (FRP is weaker in the directions perpendicular to the fiber) Selected to have: ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Fibres Three most common fibres in Civil Engineering applications: Glass Carbon Aramid (not common in North America) Required strength and stiffness Durability considerations Cost constraints Availability of materials Selected based on: ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Fibres Glass fibres: Inexpensive Most commonly used in structural applications Several grades are available: E-Glass AR-Glass (alkali resistant) High strength, moderate modulus, medium density Used in non weight/modulus critical applications ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Fibres Carbon fibres: Significantly higher cost than glass High strength, high modulus, low density E = GPa: standard E = GPa: intermediate E = GPa: high E = GPa: ultra-high Superior durability and fatigue characteristics Used in weight/modulus critical applications ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Fibres Aramid fibres: Moderate to high cost Two grades available: 60 GPa and 120 GPa elastic moduli High tensile strength, moderate modulus, low density Low compressive and shear strength Some durability concerns Potential UV degradation Potential moisture absorption and swelling ISIS EC Module 8

Here we are concerned mainly with unidirectional FRPs!
Composites For Construction Mechanical Properties Section: 1 Type of fibre and matrix FRP mechanical properties are a function of: Fibre volume content Orientation of fibres Here we are concerned mainly with unidirectional FRPs! ISIS EC Module 8

(in general versus steel): Linear elastic behaviour to failure
FRP Composites For Construction FRP vs. Steel Section: 1 Mechanical Properties FRP properties (in general versus steel): Linear elastic behaviour to failure No yielding Higher ultimate strength Lower strain at failure Comparable modulus (carbon FRP) Strain [%] 1 2 3 500 1000 1500 2000 2500 Stress [MPa] CFRP GFRP Steel ISIS EC Module 8

Quantitative Comparison
FRP Composites For Construction Quantitative Comparison Section: 1 Typical Mechanical Properties* Material Glass FRP Carbon FRP Aramid FRP Steel Ultimate Strength MPa MPa MPa MPa Elastic Modulus 30-55 GPa GPa 50-74 GPa 200 GPa Failure Strain 2-4.5 % 1-1.5 % 2-2.6 % >10 % * Based on 2001 data for specific FRP rebar products ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 FRP Physical, mechanical, durability properties of FRPs Overall properties and durability depend on: The properties of the specific polymer matrix The fibre volume fraction (i.e., volume of fibres per unit volume of matrix) The fibre cross-sectional area The orientation of the fibres within the matrix The method of manufacturing Curing and environmental exposure ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Examples of FRP Unidirectional glass FRP bar Glass FRP grid Carbon FRP prestressing tendon Glass fibre roving Carbon fibre roving ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 FRPs In the design and use of FRP materials The orientation of the fibres within the matrix is a key consideration Most important parameters for infrastructure FRPs:  Uniaxial tensile properties → strength and elastic modulus  FRP-concrete bond characteristics → transfer and carry the tensile loads  Durability ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 What is durability? The ability of an FRP material to: “resist cracking, oxidation, chemical degradation, delamination, wear, and/or the effects of foreign object damage for a specified period of time, under the appropriate load conditions, under specified environmental conditions” ISIS EC Module 8

CAUTION! Data on the durability of FRP materials is limited
Composites For Construction CAUTION! Section: 1 Data on the durability of FRP materials is limited Appears contradictory in some cases Due to many different forms of FRPs and fabrication processes FRPs used in civil engineering applications are substantially different from those used in the aerospace industry Their durability cannot be assumed to be the same Anecdotal evidence suggests that FRP materials can achieve outstanding longevity in infrastructure applications ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Durability Environments All engineering materials are subject to mechanical and physical deterioration with time, load, and exposure to various harmful environments FRP materials are very durable, and are less susceptible to degradation than many conventional construction materials ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Durability Factors affecting FRPs’ durability performance: The matrix and fibre types The relative portions of the constituents The manufacturing processes The installation procedures The short- and long-term loading and exposure condition (physical and chemical) ISIS EC Module 8

FRP Composites For Construction Introduction & Overview Section: 1 Durability Potentially harmful effects for FRP: Environmental Effects Physical Effects Moisture & Marine Environments Alkalinity& Corrosion Sustained Load: Creep DURABILITY OF FRPs Heat & Fire Cyclic loading: Fatigue Cold & Freeze-Thaw Cycling Ultraviolet Radiation POTENTIAL SYNERGIES ISIS EC Module 8

Moisture & Marine Exposures
FRP Composites For Construction Moisture & Marine Exposures Section: 2 FRPs are particularly attractive for concrete structures in moist or marine environments FRPs are not susceptible to electrochemical corrosion Corrosion of steel in conventional structures results in severe degradation HOWEVER FRPs are not immune to the potentially harmful effects of moist or marine environments ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Moisture Some FRP materials have been observed to deteriorate under prolonged exposure to moist environments Evidence linking the rate of degradation to the rate of sorption of fluid into the polymer matrix All polymers will absorb moisture Depending on the chemistry of the specific polymer involved, can cause reversible or irreversible physical, thermal, mechanical and/or chemical changes It is important to recognize that… Results from laboratory testing are not necessarily indicative of performance in the field ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Moisture Selected factors affecting moisture absorption in FRPs: Type and concentration of liquid Type of polymer and fibre Fibre-resin interface characteristics Manufacturing / application method Ambient temperature Applied stress level Extent of pre-existing damage Presence of protective coatings ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Moisture Overall effects of moisture absorption: Moisture absorption Plasticization of the matrix caused by interruption of Van der Walls bonding between polymer chains Reduced matrix strength, modulus, strain at failure & toughness Subsequently reduced matrix-dominated properties: Bond, shear, flexural strength & stiffness May also affect longitudinal tensile strength & stiffness Swelling of the matrix causes irreversible damage through matrix cracking & fibre-matrix debonding ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Moisture Typical moisture absorption trend for a matrix polymer: Time (years) 1 2 < 1% % Mass Gain ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Moisture Strength loss trend of typical FRPs due to moisture absorption: 5 10 100 % % Strength Retention Time (years) Note: no strength reductions in some lab studies Further research needed ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Potentially Important degradation synergies: Moisture absorption Sustained stress Elevated temperatures Stress-induced micro-cracking of the polymer matrix Moisture-induced micro-cracking of polymer matrix in a GFRP ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Fibres The effect of moisture on fibres’ performance: Glass fibres: Moisture penetration to the fibres may extract ions from the fibre and result in etching and pitting. can cause deterioration of tensile strength and elastic modulus Aramid fibres: Can result in fibrillation, swelling of the fibres, and reductions in compressive, shear, and bond properties. Certain chemicals such as sodium hydroxide and hydrochloric acid can cause severe hydrolysis Carbon fibres: Do not appear to be affected by exposure to moist environments ISIS EC Module 8

FRP Composites For Construction Moisture & Marine Exposures Section: 2 Resins FRPs can be protected against moisture absorption by appropriate selection of matrix materials and protective coatings: Vinylester: currently considered the best for use in preventing moisture effects in infrastructure composites Epoxy: also considered adequate Polyester: Available research also suggests poor performance and should typically not be used ISIS EC Module 8

Alkalinity & Corrosion
FRP Composites For Construction Alkalinity & Corrosion Section: 3 Alkalinity Effects of alkalinity on FRPs’ performance: The pH level inside concrete is > 11 (i.e., highly alkaline) Becomes important for internal FRP reinforcement applications within concrete (particularly for GFRP) pH > 11 Protection by matrix Level of applied stress Temperature Damage to glass fibres depends on GFRP bar ISIS EC Module 8

FRP Composites For Construction Alkalinity & Corrosion Section: 3 Alkalinity Degradation mechanisms for GFRP reinforcement: Reduction in tensile properties Damage at the fibre-resin interface Alkaline solutions cause embrittlement of the fibres Alkaline solutions GFRP bar ISIS EC Module 8

FRP Composites For Construction Alkalinity & Corrosion Section: 3 Alkalinity The effect of alkaline environments on fibres: E-glass fibres Strength reduction of 0 – 75 % of initial values AR-glass fibres Significant improvement in alkaline environments, but $$$ Aramid fibres Strength reduction of 10 – 50 % of initial values Need further research Carbon fibres Strength reduction of 0 – 20 % of initial values ISIS EC Module 8

FRP Composites For Construction Alkalinity & Corrosion Section: 3 Corrosion Galvanic Corrosion: FRPs are not susceptible to electrochemical corrosion Certain FRPs (e.g., CFRPs) can contribute to increased corrosion of metal components through galvanic corrosion Galvanic corrosion = accelerated corrosion of a metal due to electrical contact with a nonmetallic conductor in a corrosive environment ISIS EC Module 8

FRP Composites For Construction Alkalinity & Corrosion Section: 3 Corrosion Guarding against galvanic corrosion: CFRPs should not be permitted to come in to direct contact with steel or aluminum in structures Internal reinforcement: place plastic spacers between steel and CFRP bars Steel bar CFRP bar Spacer External strengthening: apply a thin layer of epoxy or GFRP sheet between CFRP and steel Steel girder GFRP sheet CFRP sheet ISIS EC Module 8

High Temperatures & Fire
FRP Composites For Construction High Temperatures & Fire Section: 4 FRP materials are now widely used for reinforcement and rehabilitation of bridges and other outdoor structures FRPs have seen comparatively little use in building applications FRP materials are susceptible to elevated temperatures Several concerns associated with their behaviour during fire or in high temperature service environments Extremely difficult to make generalizations regarding high temperature behaviour Large number of possible fibre-matrix combinations, manufacturing methods, and applications ISIS EC Module 8

FRP Composites For Construction High Temperatures & Fire Section: 4 FRPs used in infrastructure applications suffer degradation of mechanical and/or bond properties at temperatures exceeding their glass transition temperature Glass transition temperature, Tg the midpoint of the temperature range over which an amorphous material (such as glass or a high polymer) changes from (or to) brittle, vitreous state to (or from) a rubbery state (ACI ) All organic polymer materials combust at high temperatures Most matrix polymers release large quantities of dense, black, toxic smoke ISIS EC Module 8

FRP Composites For Construction High Temperatures & Fire Section: 4 Potential problems of FRPs under fire: Internal FRP reinforcement External FRP strengthening Sudden and severe loss of bond at T > Tg Too thin for self-insulating layer, loss of bond at T > Tg ISIS EC Module 8

FRP Composites For Construction High Temperatures & Fire Section: 4 Mechanical properties of FRPs deteriorate with increasing temperature “Critical” temperature commonly taken to be Tg for the polymer matrix Typically in the range of ºC Exceeding Tg results in severe degradation of matrix dominated properties such as transverse and shear strength and stiffness Longitudinal properties also affected above Tg Tensile strength reductions as high as 80% can be expected in the fibre direction at temperatures of only 300ºC Important that an FRP component not be exposed to temperatures close to or above Tg during the normal range of operating temperatures ISIS EC Module 8

FRP Composites For Construction High Temperatures & Fire Section: 4 Degradation of mechanical properties is mainly governed by the properties of the matrix: Carbon fibres No degradation in strength and stiffness up to 1000 ºC Glass fibres 20-60% reduction in strength at 600 ºC Aramid fibres 20-60% reduction in strength at 300 ºC ISIS EC Module 8

FRP Composites For Construction High Temperatures & Fire Section: 4 Deterioration of mechanical and bond properties for GFRP bars: Critical temperature (T > Tg) ISIS EC Module 8

FRP Composites For Construction High Temperatures & Fire Section: 4 The use of FRP internal reinforcement is currently not recommended for structures in which fire resistance is essential to maintain structural integrity Exposure to elevated temperatures for a prolonged period of time may be a concern with respect to exacerbation of moisture absorption and alkalinity effects ISIS EC Module 8

FRP Composites For Construction Cold Temperatures Section: 5 Potential for damage due to low temperatures and thermal cycling must be considered in outdoor applications Freezing and freeze-thaw cycling may affect the durability performance of FRP components through: Changes that occur in the behaviour of the component materials at low temperatures Differential thermal expansion between the polymer matrix and fibre components between concrete and FRP materials Could result in damage to the FRP or to the interface between FRP components & other materials ISIS EC Module 8

FRP Composites For Construction Cold Temperatures Section: 5 Exposure to subzero temperature may result in residual stresses in FRPs due to matrix stiffening and different CTEs between fibres and matrix Stiffness Strength Dimensional stability Fatigue resistance Moisture absorption Resistance to alkalinity Matrix micro-cracking and fibre-matrix bond degradation May affect FRPs’ ISIS EC Module 8

HOWEVER Cold Temperatures Increasing # of freeze/thaw cycles
FRP Composites For Construction Cold Temperatures Section: 5 Increased severity of matrix cracks Increased matrix brittleness Decreased tensile strength Increasing # of freeze/thaw cycles HOWEVER The effects on FRP properties appear to be minor in most infrastructure applications ISIS EC Module 8

Ultraviolet Radiation
FRP Composites For Construction Ultraviolet Radiation Section: 6 Ultraviolet (UV) radiation damages most polymer matrices Aramid fibres: significant Glass fibres: insignificant Carbon fibres: insignificant The effects of UV on: Thus, potential for UV degradation is important when FRPs are exposed to direct sunlight ISIS EC Module 8

FRP Composites For Construction Ultraviolet Radiation Section: 6 Photodegradation: UV radiation within a certain range of specific wavelengths breaks chemical bonds between polymer chains and resulting in: Discoloration Surface oxidation Embrittlement Microcracking of the matrix UV-induced surface flaws can cause: Stress concentrations → may lead to premature failure Increased susceptibility to damage from alkalinity & moisture ISIS EC Module 8

FRP Composites For Construction Ultraviolet Radiation Section: 6 Combined effects of UV and moisture on FRP bars: CFRP: tensile strength reduction of 0-20 % GFRP: tensile strength reduction of 0-40 % AFRP: tensile strength reduction of 0-30 % Protection of FRPs from UV radiation: UV resistant paints Coatings Sacrificial surfaces UV resistant polymer resins ISIS EC Module 8

FRP Composites For Construction Creep & Creep Rupture Section: 7 Creep: A behaviour of materials wherein an increase in strain is observed with time under a constant level of stress (L = final length) L1 L1 P Steel P P Steel P P = P L = L1 P = P L > L1 ideal with creep ISIS EC Module 8

FRP Composites For Construction Creep & Creep Rupture Section: 7 Relaxation: a reduction in stress in a material with time at a constant level of strain (P = final load) L1 L1 P P P P 1 1 Steel Steel P = P L = L1 P > P1 L = L1 ideal with relaxation ISIS EC Module 8

Thus, creep is potentially important for FRP
Composites For Construction Creep & Creep Rupture Section: 7 Creep Effects of creep on the performance of FRPs: Fibres → relatively insensitive to creep in absence of other harmful durability factors Matrices → highly sensitive to creep Thus, creep is potentially important for FRP (Because loads must be transferred through the matrix) ISIS EC Module 8

Creep & Creep Rupture For good performance under sustained loads:
FRP Composites For Construction Creep & Creep Rupture Section: 7 Creep For good performance under sustained loads: Use an appropriate matrix material Take care during the fabrication and curing processes Creep behaviour of different FRP materials is complex and depends on: Specific constituents and fabrication Type, direction, and level of loading applied Exposure to other durability factors such as alkalinity, moisture, thermal exposures Few standard test methods for creep testing FRP materials Difficult to make generalizations about FRPs’ creep performance ISIS EC Module 8

Called Stress Rupture, Creep Rupture, or Stress Corrosion
FRP Composites For Construction Creep & Creep Rupture Section: 7 Creep Rupture Under certain conditions… creep can result in rupture of FRPs at sustained load levels that are significantly less than ultimate Called Stress Rupture, Creep Rupture, or Stress Corrosion Creep rupture is influenced largely by the types of fibres and susceptibility to alkaline environments (glass FRPs in particular) ISIS EC Module 8

FRP Composites For Construction Creep & Creep Rupture Section: 7 Endurance time: the time to creep rupture of FRPs under a given level of sustained load Sustained stress Ultimate strength Endurance time Other factors influencing endurance time include: Elevated temperature Alkalinity Moisture Freeze-thaw cycling UV exposure Endurance time ISIS EC Module 8

FRP Composites For Construction Creep & Creep Rupture Section: 7 Creep rupture stress limits for FRP reinforcing bars (50 years creep rupture strength) : GFRP: % of initial tensile strength AFRP: % of initial tensile strength CFRP: % of initial tensile strength Note: Laboratory testing is not necessarily representative of field performance ISIS EC Module 8

FRP Composites For Construction Fatigue Section: 8 Fatigue: all structures are subjected to repeated cycles of loading and unloading due to: Traffic and other moving loads Thermal effects (differential thermal expansion) Wind-induced or mechanical vibrations Fatigue performance of most FRPs is as good as or better than steel ISIS EC Module 8

Fatigue Good fatigue performance of FRPs depends on:
Composites For Construction Fatigue Section: 8 Good fatigue performance of FRPs depends on: Toughness of the matrix Ability to resist cracking Performance of FRPs under fatigue load: CFRP: best GFRP: good AFRP: excellent NOTE: Fatigue performance of FRP reinforced concrete appears to be best when GFRP reinforcement is used ISIS EC Module 8

FRP Composites For Construction Reduction Factors Section: 9 Numerous factors exist that can potentially affect the long term durability of FRP materials in civil engineering and construction applications Durability factors remain incompletely understood Reduction factors in existing design codes and recommendations: Applied to the nominal stress and strain capacities of FRPs limit the useable ranges of stress and strain in engineering design ISIS EC Module 8

Reduction Factors (FRP bars)
Composites For Construction Reduction Factors (FRP bars) Section: 9 For non-prestressed FRPs Document Material Exposure Condition Reduction Factor CHBDC, 2006 AFRP All 0.60 CFRP All 0.75 GFRP All 0.50 CSA S806-02 All All 0.75 ACI 440.1R-06 AFRP Not exposed to earth and weather 0.90 Exposed to earth and weather 0.80 CFRP Not exposed to earth and weather 1.00 Exposed to earth and weather 0.90 GFRP Not exposed to earth and weather 0.80 Exposed to earth and weather 0.70 ISIS EC Module 8

Stress limit (% of ultimate)
FRP Composites For Construction Reduction Factors Section: 9 Sustained (service) stress levels are limited to avoid creep rupture and other forms of distress: Document FRP Bars Stress limit (% of ultimate) CHBDC, 2006 AFRP 35 CFRP 65 GFRP 25 CSA S806-02 GFRP 30 ACI 440.1R-06 AFRP 30 CFRP 55 GFRP 20 ISIS EC Module 8

Specifications: Durability of FRP Bars
Composites For Construction Specifications: Durability of FRP Bars Section: 10 ISIS Canada has recently published a product certification document: Specifications for Product Certification of Fibre Reinforced Polymers (2006) Test methods are given for quantitatively defining the durability of FRP reinforcing bars for concrete Classifies FRP bars into different durability “categories” (e.g. D1, D2, etc.) ISIS EC Module 8

Specifications: Durability Criteria
FRP Composites For Construction Specifications: Durability Criteria Section: 10 Property Specified limits Void content ≤ 1% Water absorption ≤ 1% for D2 FRP bars and grids; ≤ 0.75% for D1 bars and grids Cure ratio ≥ 95% for D2 bars and grids; ≥ 98% for D1 bars and grids Glass transition temperature DMA = 90°C, DSC = 80°C for D2 bars and grids; DMA = 110°C, DSC = 100°C for D1 bars and grids Alkali resistance in high pH solution (no load) Tensile capacity retention ≥70% for D2 bars and grids; tensile capacity retention ≥80% for D1 bars and grids Alkali resistance in high pH solution (with load) Tensile capacity retention ≥60% for D2 bars and grids; tensile capacity retention ≥70% for D1 bars and grids Creep rupture strength Creep rupture strength: ≥35% UTS (Glass) ≥75% UTS (Carbon) ≥45% UTS (Aramid) Creep Report creep strain values at 1000 hr, 3000 hr and hr Fatigue strength Fatigue strength at 2 million cycles: ISIS EC Module 8

Case Study: Field Evaluation of GFRP
Composites For Construction Case Study: Field Evaluation of GFRP Section: 11 Laboratory experiments have suggested that FRPs may be susceptible to deterioration under many environmental conditions Field data are scant for FRPs used in infrastructure applications Available field data indicate that in-service performance can be much better than assumed on the basis of laboratory testing ISIS EC Module 8

Composites For Construction Case Study: Field Evaluation of GFRP Section: 11 ISIS Canada Research project to study in-service performance of glass FRP reinforcing bars in concrete structures in Canada: Joffre Bridge (Sherbrooke, Quebec) Crowchild Bridge (Calgary, Alberta) Hall’s Harbour Wharf (Hall’s Harbour, Nova Scotia) Waterloo Creek Bridge (British Columbia) Chatham Bridge (Ontario) Samples studied for evidence of deterioration using various optical and chemical techniques ISIS EC Module 8

Composites For Construction Case Study: Field Evaluation of GFRP Section: 11 There are many methods to investigate durability performance of GFRP reinforcing bars: Optical Microscopy (OM) Scanning Electron Microscopy (SEM) Energy Dispersive X-ray Analysis (EDX) Infrared Spectroscopy (IS) Differential Scanning Calorimetry (DSC) ISIS EC Module 8

Field Evaluation of GFRP
Composites For Construction Field Evaluation of GFRP Section: 11 Case study Optical Microscopy (OM): To visually examine the interface between the GFRP reinforcing bars and the concrete After 8 years of exposure to alkalinity, freeze-thaw, wet-dry, and chlorides Interface Interface Crowchild Trail Bridge Chatham Bridge No evidence of damage or deterioration ISIS EC Module 8

Composites For Construction Field Evaluation of GFRP Section: 11 Case study Scanning Electron Microscopy (SEM): To conduct highly detailed visual examination of GFRP After 8 years of exposure to alkalinity, freeze-thaw, wet-dry, and chlorides Crowchild Trail Bridge Chatham Bridge No evidence of damage or deterioration ISIS EC Module 8

Composites For Construction Field Evaluation of GFRP Section: 11 Case study Energy Dispersive X-ray Analysis (EDX): To determine if any chemical changes had occurred in glass fibres or in polymer matrix After 8 years of exposure to alkalinity, freeze-thaw, wet-dry, and chlorides No Sodium or Potassium are present ISIS EC Module 8

Composites For Construction Field Evaluation of GFRP Section: 11 Case study Other techniques… Infrared Spectroscopy (IS): to determine the extent of alkali-induced hydrolysis of the matrix No evidence of damage or deterioration Differential Scanning Calorimetry (DSC): to determine the glass transition temperature of a polymer material ISIS EC Module 8

Durability Research Needs
FRP Design with reinforcement Durability Research Needs The durability performance of FRP materials is generally very good in comparison with other, more conventional, construction materials However, it should be equally clear that the long-term durability of FRPs remains incompletely understood A large research effort is thus required to fill all of the gaps in knowledge ISIS EC Module 8

FRP Design with reinforcement Durability Research Needs Moisture: Effects of under-cure and/or incomplete cure of the polymer matrix Effects of continuous versus intermittent exposure to moisture when bonded to concrete Alkalinity: Determination of rational and defensible standard alkaline solutions and alkalinity testing protocols and database of durability information Development of an understanding of alkali-induced deterioration mechanisms The potential synergistic effects of combined alkalinity, stress, moisture, and temperature are not well understood, particularly as they relate to creep-rupture of FRP components. ISIS EC Module 8

FRP Design with reinforcement Durability Research Needs Fire: Non-destructive evaluation methods for fire-exposed composites Fire repair strategies Development of relationships between tests on small scale material samples at high temperature and full-scale structural performance during fire Fatigue: More fatigue data on a variety of FRP materials Mechanistic understanding of fatigue in composites in conjunction with various environmental factors Development of a rational and defensible short term representative exposure to evaluate long-term fatigue performance ISIS EC Module 8

FRP Design with reinforcement Durability Research Needs Synergies: Potentially important synergies between most of the durability factors considered in this module remain incompletely understood Research needed to elucidate the interrelationships between moisture, alkalinity, temperature, stress, and chemical exposures ISIS EC Module 8

Additional Information
FRP Design with reinforcement Additional Information Additional information on all of the topics discussed in this module is available from: ISIS EC Module 8

Durability of FRP Composites for Construction

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